Tape reels which are incorporated in tape cassettes, such as video tape cassettes, are typically constructed in a manner such as shown in Figs. 1A and 1B. Specifically, the conventional tape reels include a reel hub 100 and a reel flange 102 having a deposition rib 104 formed on an end surface thereof opposite to the reel hub 100. Reel hub 100 and reel flange 102 are integrally joined to one another by thermal or ultrasonic welding of deposition rib 104 or other similar joining means.
The connection of reel hub 100 to reel flange 102 by ultrasonic welding is carried out while forcibly pressing against the central portion of deposition rib 104 by means of the horn of an ultrasonic welding machine and regulating the vertical position of the reel flange 102 with respect to the reel hub 100 by means of the upper end of the outer periphery of the reel hub 100. In ribs having the conventional structure of deposition rib 104, a melt 106 formed by melting the deposition rib 104 fails to spread uniformly between the reel hub 100 and the reel flange 102 so that the melt 106 on one side of deposition rib 104 has a significantly different thickness than the melt 106 on the opposite side of deposition rib 104. As a result, the reel flange 102 is joined to the reel hub 100 at an oblique angle, as shown in FIG. 1B.
Unfortunately, the inclination of the reel flange 102 with respect to reel hub 100 causes sufficient deflection and/or warpage to occur at the outer periphery of the reel flange 102 so that a tape reel of inferior quality is produced. As a result, quality control in the production of such tape reels is highly troublesome causing poor production yields. Moreover, this process causes significant variations in the pressure exerted by the horn of the ultrasonic welding machine on the deposition rib 104, thereby leading to joining failures. As a result of the foregoing, it is apparent that the structure of conventional tape reels hinders productivity.
Thus, the need exists for a tape reel for tape cassettes which is capable of being manufactured at high speeds in highly simplified processes which are capable of achieving high yields.